Indicates that the drift line calculation will begin at some of the boundaries of the drift area as set by AREA.
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Requests that the electrons or ions start to drift from the surfaces of the wires that have been SELECTed. Electrons are usually not produced near the wires and they are therefore drifted by default 'in reverse', i.e. with a positive charge. The resulting plot shows the origin of all electrons that can end up on the wire. Since ions are normally produced near the wire surface, they are drifted in their usual mode, i.e. with a positive charge. The resulting plot therefore shows where ions go that are produced in an avalanche at the wire. To modify this behaviour, i.e. to study electrons drifting away from wires that repel electrons and ions drifting away from wires that attract ions, use the POSITIVE and NEGATIVE options.
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Indicates that the drift line calculation will begin on the track. The appearance of the resulting plot depends to a large extent on the format of the TRACK command that you have used: - electron or ion drift lines from a user determined number of regularly spaced points along a track (TRACK FIXED) - electron drift lines from randomly distributed points along the track, including cluster formation (TRACK EXPONENTIAL) - electron drift lines from the points where a particle traversing the chamber ionised the gas, including or not delta and Auger electrons, photo ionisation and multiple scattering (TRACK HEED) Although permitted, the ION option has no meaning used together with the latter two TRACK formats.
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Indicates that the drift line are calculated from the zeros of the electrostatic field, both in the attracting and in the repelling directions. The ELECTRON/ION and POSITIVE/NEGATIVE settings are ignored. This choice is useful when you're determining the precise acceptance boundaries for each of the wires. Note: zero finding is not available yet in the default version of Garfield.
Requests the use of the Monte Carlo drift line integration routine rather than the Runge-Kutta-Fehlberg integration routine. This option is particularly interesting used in conjuction with the more realistic variants of the DRIFT TRACK command.
Requests calculation and plotting of isochrones. You must specify the interval, in microsec, after the ISOCHRONES keyword. The appearance of the isochrones is affected by: - the polyline and the polymarker representations ISOCHRONES, see the graphics !REPRESENT command for further information; - by a series of options which control whether the points on the isochrones are to be joined by lines or simply to be marked, up to which distance isochrone points may be joined, whether checks have to be made for intersects between isochrones and drift lines, see the &DRIFT INTEGRATION-PARAMETERS command for details. Plotting isochrones can be a CPU intensive operation, depending on the number of drift lines, the number of isochrones and the options that have been chosen. In order to plot only the isochrones and not the drift lines, one uses ISOCHRONES in conjunction with NOLINE-PLOT. The drift time used for the isochrones is measured from the wire or the solid where the electron or ion ends up. Isochrones are only plotted for electrons and ions that do reach a wire or a solid. Isochrones are not plotted for particles that reach a replica of a wire (in case of periodic chambers). Note that isochrones can also be obtained with two other commands: TABLE CONTOUR and PLOT CONTOUR TIME. The latter two commands are do not take the end-point of the electrons into account, and as a result may produce isochrones joining points leading to different wires or solids. [Isochrones are by default not plotted.]
Requests plotting of the drift lines. You may wish to switch this option off if you want to see only isochrones. This option is initially on.
Requests printing of drift line summary data. This option is not compatible with LINE-PLOT in interactive VM/CMS (because of system shortcomings) unless the output has been rerouted (> dsname). This option is initially off.
Requests drifting of electrons.
Requests drifting of ions.
By default, electrons are drifted with negative charge and ions with positive charge. If you wish to see the origin of the electrons and ions arriving at a given position, you may wish to reverse the sign. The POSITIVE option forces the charge to be positive, no matter whether the particle is an electron or an ion.
By default, electrons are drifted with negative charge and ions with positive charge. If you wish to see the origin of the electrons and ions arriving at a given position, you may wish to reverse the sign. The NEGATIVE option forces the charge to be negative, no matter whether the particle is an electron or an ion.